Adjusting recrystallization kinetics of WNiCo alloy by intensive shear strain

The study investigates the effects of intensive shear strain processing, performed by selected regimes of rotary swaging, on recrystallization kinetics and deformation behaviour of a WNiCo tungsten heavy alloy. The results of uniaxial hot compression tests and thorough microstructure observations indicate that the selected rotary swaging regime, especially the swaging temperature, influences significantly not only the occurrence and development of dynamic hardening/softening processes, which consequently influence the flow stress, but also the recrystallization kinetics as such. The deformation temperature of 1100 °C was sufficient to initiate dynamic recrystallization in the NiCo matrix, the average grain size within which decreased down to 1.9 μm. The deformation temperature of 1200 °C caused further softening within the matrix and intensified its plastic flow, which also supported joining of W agglomerates. Particularly the high swaging temperatures in combination with high strain rates (100 s⁻¹) imparted flow stress maxima exceeding 1100 MPa. From the computational perspective, the complex effect of the occurring structure-forming phenomena on the behaviour of the WNiCo alloy was mapped by creating a rheological model, predicting its flow stress development under a wide range of temperatures. The rheological model was created via a regression analysis on the experimental data, and can serve as a basis for prospective numerical simulations using the finite element method.